The diagram in figure shows a device which makes use of the principle of transmission of pressure. (i) Name the parts labelled by the letters X and Y. (ii) Describe what happens to the valves A and B and to the quantity of water in the two cylinders when the lever arm is moved down. (iii) Give reasons for what happens to the valves A and B in part (ii). (iv) What happens when the release valve is opened ? (v) What happens to the valve B in cylinder P when the lever arm is moved up ? (vi) Give a reason for your answer in part (v) (vii) State one use of the above device.

(i) The parts are —

X → Press plunger

Y → Pump plunger

(ii) When the lever arm is moved down, valve B closes and valve A opens, so water from cylinder P is forced into cylinder Q.

(iii) When the lever arm is moved down, valve B closes due to an increase in pressure in cylinder P. Now pressure from cylinder P is transmitted to the connecting pipe. As the pressure in the connecting pipe becomes greater than cylinder Q, valve A opens, so water from cylinder P is forced into cylinder Q.

(iv) When the release valve is opened the ram (or press) plunger Q gets lowered and water of the cylinder Q runs out into the reservoir.

(v) When the lever arm is moved up valve B opens upwards.

(vi) When the lever arm is moved up valve B opens upward because the pressure in cylinder P decreases.

(vii) A hydraulic press is used for pressing cotton bales and goods like quilts, books, etc.